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Hemolysis is a potential limitation of percutaneously delivered left‐sided mechanical circulatory support pumps, including trans valvular micro‐axial flow pumps (TVP). Hemolytic biomarkers among durable left ventricular assist devices include lactate dehydrogenase (LDH) >2.5 times the upper limit of normal (ULN) and plasma‐free hemoglobin (pf‐Hb) >20 mg/dL. We examined the predictive value of these markers among patients with cardiogenic shock (CS) receiving a TVP. We retrospectively studied records of 116 consecutive patients receiving an Impella TVP at our institution between 2012 and 2017 for CS. Twenty‐three met inclusion/exclusion criteria, and had sufficient pf‐Hb data for analysis. Area under receiver‐operator characteristic (ROC) curve for diagnosing hemolysis were calculated. Mean age was 62 ± 14 years and ejection fraction was 15 ± 5%. Mean duration of support was 5.4 ± 3.5 days. Pre‐device LDH levels were >2.5x ULN in 71% (n = 5/7) of 5.0 and 29% of CP patients, while pre‐device pf‐Hb levels were >20 mg/dL in 14% (n = 1/7) of 5.0 and 25% (n = 4/16) of CP patients. Given elevated baseline LDH and pf‐Hb levels, we defined hemolysis as a pf‐Hb level >40 mg/dL within 72 h post‐implant plus clinical evidence of device‐related hemolysis. We identified that 30% (n = 7/23) had device‐related hemolysis. Using ROC curve‐derived cut‐points, an increase in delta pf‐Hb by >27mg/dL, not delta LDH, within 24 h after TVP implant (delta pf‐Hb: C‐statistic = 0.79, sensitivity: 57%, specificity: 93%, p <0.05) was highly predictive of hemolysis. In conclusion, we identified a change in pf‐Hb, not LDH, levels is highly sensitive and specific for hemolysis in patients treated with a TVP for CS. [ABSTRACT FROM AUTHOR]